1. Field of the Invention
The invention relates to a device for covering a core of a foothold with a synthetic resin which device comprises a lower mold for holding the core of the foothold and an upper mold for covering the upper portion of the core.
2. Related Art
There is a conventional device for covering a U-shaped core of a foothold with a synthetic resin which device comprises a lower mold for holding the core of the foothold and an upper mold for covering the upper portion of the core, as shown in FIG. 4, wherein a core 31 for the foothold which is placed on a lower mold 30 is held in a floating state by a plurality of interval holding members 32, 32, . . . respectively made of a synthetic resin and arranged at side portions and a tread of the foothold, and the synthetic resin is supplied to the outer periphery of the core 31 for the foothold by an injection molding assembly 33 so as to cover the core 31 for the foothold with the synthetic resin.
However, when the core 31 for the foothold is held in a floating state, the interval holding members 32, 32, . . . have to be manufactured in advance by a synthetic resin, and some interval holding members arranged on the side portions are different in a shape from those arranged on the tread, and hence the interval holding members 32, 32, . . . were difficult to be manufactured and troublesome to be attached to the core 31. Further, when the core of the foothold is covered with the synthetic resin by this conventional device shown in FIG. 4, a synthetic resin 34 for covering the core 31 is not mixed with a synthetic resin of the interval holding members 32, 32, . . . at the portion where the interval holding members 32, 32, . . . as shown in FIG. 5 are attached to the side portions and the tread, causing a problem that the strength at that portion becomes weak. Further, since the synthetic resin 34 is prevented from flowing by the attachment of the interval holding members 32, 32, . . . , it was necessary to provide a plurality of supply passages 35 of the synthetic resin 34.
The invention has been made in view of the foregoing problems of the prior art, and it is an object of the invention to provide a device for covering a core of a foothold with a synthetic resin capable of certainly and easily holding the core for the foothold in a floating state, enabling one supply passage to supply a synthetic resin so as to cover the outer periphery of the core for the foothold with the synthetic resin, eliminating a surface where synthetic resins are mixed with each other as made in the prior art (namely, the mixture of the synthetic resin of the interval holding members 32, 32, . . . and that of the synthetic resin 34) so as to manufacture a strong foothold.
To achieve the above objects, the device for covering the core of the foothold with a synthetic resin comprises a lower mold for holding the core of the foothold, an upper mold for covering the upper portion of the core, wherein a plurality of pins stand upright on the lower mold, which pins are urged by springs at portions corresponding to a tread and leg portions of the foothold, pistons for fixing the core to portions in the vicinity of both ends of the portion corresponding to the tread are provided in the back and forth direction of the core while opposing the core, a supply port of a synthetic resin is defined in the upper mold, and a supply passage for supplying the synthetic resin is defined in the boundary between the upper and lower molds at the outer peripheral surface of the core.